In a previous HVEM study we described the first cell-free system, based on homogenates of surf clam oocytes, that executes centriole formation and duplication. Because centrioles are extremely small (0.25 by 0.5 um), the only way their morphology and replication can be studied is with the EM. In this context one of us (Dr. Rieder) has clearly demonstrated that HVEM of serial thick sections greatly facilitates studies on centrosome location, numbers and strucsture. This is an ongoing collaborative effort between Drs. Palazzo and Rieder with the aim of understanding centrosome structure, biochemistry and function. At the moment we are generating 3-D tomographic reconstructions of centrosomes formed in-vivo to compare with similar centrosomes formed in the presence of antibodies to specific centrosomal proteins. The goal here is to localize particular centrosomal proteins within the centrosome.